What is the definition of phase lag and phase difference?

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1. Jan 30, 2016

ajaysabarish

what is the definition of phase lag and phase difference in waves and how are these 2 related?please explain in simple words and with real life examples.
Please explain phase,phase lag and phase difference from scratch.

Last edited: Jan 30, 2016
2. Jan 30, 2016

blue_leaf77

The two terms can be used interchangeably. Phase lag is usually more used to describe the phase difference arising between two propagating waves like laser or sound wave. Suppose two laser are fired at the same time, in the path of one of the laser, one places a glass of certain length. A phase lag between the two lasers will arise when one of the laser is retarded because of the propagation in the glass. Nevertheless, I don't think there is that much difference in between the usage of the two terms.

3. Jan 30, 2016

ajaysabarish

Sir,but what is the actual definition of phase and phase lag,without understanding it,it is very difficult to understand your answers.Atleast suggest some website or video letures which explains these 2 terms from scratch.

4. Jan 30, 2016

blue_leaf77

Suppose you have a sinusoidal oscillation of the form $y(\phi_1) = A_1\sin \phi_1$, the argument of the sine function, $\theta$ is called the phase. When now you have one more oscillation $y(\phi_2) = A_2\sin\phi_2$ and calculate the phase difference between it and the previous oscillation, it will be $\Delta \phi = \phi_2-\phi_1$. For example see . That is just one of many youtube items which result when you type "phase difference" in its browser box.